Explosive separable nut



APII 6, 1965 w. R. DlcKlE 3,176,573

EXPLOSIVE SEPARABLE NUT Filed Nov. 6. 1961 nwe/lw 4 TTORNE Y `in theart.

United StatesPatent Ofice atraen 3,176,573 EXPLGSIVE SEPARABLE NUTWilliam R. Dickie, Manhattan Beach, Calif., assigner to Hit-ShearCorporation, Torrance, Calif., a corporation of California Filed Nov. 6,1961, Ser. No. 150,305 6 Claims.V (Cl. 85-33) This invention relates toa separable nut adapted to make an engagement with a threaded shankmember and to be separated therefrom by fluid force.

Separable nuts which include individual nut segments,

each of which bears a fragment of a thread, and which are held togetherby a removable retainer, are known However, the problems left unsolvedby the known devices are that they areY difficult to manufacture, andare unreliable in operation, unless manufactured to very closetolerances, and with considerable complexity. Accordingly, explosivelyseparable nuts have not been widely used except in applications wherethe absence of an alternative type of mechanism coupled with the needfor high reliability in operation justified the use of an expensiveitem.

It is an object of this invention to provide a separable nut which isreliable in its operation, and which invention includes a new and novelmeans for making separable nuts which enables the device to beinexpensively and, at the same time, reliably manufactured. Theinvention thereby makes available to the manufacturing arts aneconomically feasible and reliable device, and promises to open up manynew uses for separable nuts.

A separable nut according to this invention comprises a retainer with achamber therein defined by an interior wall. An axial passage extendsthrough this wall in communication with the chamber, the passage beingdefined by a boundary. There is a shoulder in the chamberV adjacentto-the passage. Y

A plurality of axially aligned and spaced apart nut segments is providedin the passage, and each of these segments includes a thread-bearingportion which carries a respective thread fragment. Each segment alsoincludes a cam-bearing portion positioned inside the chamber which bearsa cam surface adapted to strike the shoulder in order to cam the threadfragments off of engaging threads on a shank member to which the nut isattached in use.

There is a clearance between all adjacent ones of the nut segments andthe passage boundary, and this clearance is filled with settable,extrudable, encapsulating material which holds the segments in positionwith the thread fragments arranged to receive` the thread of a shankmember.

A squib is provided in the chamber for releasing gases to build uppressure and for separating the nut which forces the cam` surfacestoward the shoulder to carry out the aforesaid camming and releaseaction.

Instead of an explosive squib, it is possible to utilize other types ofdevices, which can also properly be denoted as'squibs in the sense thata uid is self-contained at a point of use, and is suddenly released suchas, for example, by provision of a CO2 cartridge and a point forpuncturing the same. This 4is a squib in the same sense as the explosivesquib, because both devices quickly release gases from a self-containedsource which is in iiuid communication with the expansible chamber.Y

The method according to this invention for manufacturing the abovedevice comprises providing an externally fiuted element having aplurality of arms with axial striations between them; placing theelement at least partially in the passage with clearance between it andthe boundary; and then encapsulating it in that location with the saidPatented Apr. 6, 1965 encapsulating material. After the encapsulatingmaterial has set, the central portion of the fluted element is drilledout and the resulting hole is thread-tapped, thereby forming a pluralityof individual segments and, at the same time, cutting the respectivethread fragments in the segments, which fragments will then lie inperfect alignment with each other.

The above and other features of this invention will be fully understoodfrom the following detailed description and the accompanying drawings inwhich:

FIG. 1 is a cross-section of a portion of the presently preferredembodiment of the invention taken at line 1-1 of FIG. 2;

FIG. 2 is a left-hand end view of FIG. l;

FIG. 3 is a side View partly in cutaway cross-section as still anotherpart of the invention;

FIG. 4 is a left-hand end view of FIG. 3;

FIG. 5 is a side elevation of a tinted element forming an intermediatestructural part in the manufacture of the device;

FIG. 6 is a right-hand end View of FIG. 5;

FG. 7 is a side elevation partly in cutaway cross-section showing thepresently preferred embodiment of the invention; and

FIG. 8 is a left-hand end view of FIG. 7.

A separable nut lil according to the invention is best shown in FIGS. 7and 8. Its principal parts include a retainer 11, a nut 12, a plug 13,and a squib 14.

ln FIG. 1, retainer 11 is shown in detail. It has a central axis 15 atone end of which a port 16 opens into a chamber 17. The chamber is denedby an interior wall 18. A passage 19 extends axially through theinterior wall, and is defined by a boundary Ztl. Axiallyextending teeth2i project into the passage from the boundary.

A shoulder 22 is disposed in the chamber adjacent to the passage. Anexternally-threaded plug 13 is adapted to be threaded luto port 16 toclose the right-hand end of the chamber. A threaded hole 26 extendsaxially through the plug to receive and hold squib 14, the squib beingadapted to discharge gases into a bore 27 in the plug, which in turn 1sin fluid communication with the chamber. The squib has leads 28 forconducting firing current thereto.

As best shown in FIGS. 7 and 8, nut 12 comprises four segments 30, 31,32, 33, which are radially spaced apart from each other and are axiallyaligned, a portion of each of them standing in the passage, and anotherportion standing in the chamber. Besides being spaced apart from eachother, the segments are also spaced from boundary 20 and from the teethso that there is a continuous peripheral clearance 34 between theboundary, teeth and segments.

Clearance 34 is filled with an extrudable, settable, encapsulatingmaterial 35. The presently preferred material is di-allyl phthalatemolding compound, mineral filled, preferably with an asbestos filler.This material will set hard enough to resist torque forces but, underpressure, is extrudaole for purposes which will later become evident.EncapsulatingV material 35 serves to hold segments liu-33 in place, andforms a gas-seal around the segments.

Each individual segment, of which segment 3f) is typical and shown indetail, includes a thread-bearing portion 36 which carries a threadfragment 37 on its inside surface and a cam-bearing portion 33 with anexternal cam surface 39 thereon. Cam surface 39 is a fragment ofV aconical frusturn. It overhangs, and is adapted to strike, shoulder 22..A relief itl is formed inside the cam-bearing portion. The relief formsa junction 41 with the 3 thread fragments, which junction acts as afulcrum in a manner later to be described.

The construction of the completed nut is shown in FIGS. 7 and 8 andshould be evident from the above. The method of constructing this nut,which is a feature of the invention, will be best understood byconsideration of FIGS. 5 and 6, which both show an externally flutedelement 45 with four arms, 46, 47, 4S, 49. These arms will be formedinto segments StB-33, respectively. This fluted element is easily formedby turning it on a lathe and then cutting axial notches 50, 51, 52, 53,which have root lines 54, 55, S6, 57, respectively. This fluted elementis placed inside the retainer and held in the position shown in FIG. 7.Then the encapsulating material is placed as shown in FIGS. 7 and 8 andpermitted to set. The fluted element is thereby firmly held againstrotation, the teeth serving to hold the encapsulating material againstrotation and this resistance is, of course, transmitted to the segmentsthemselves.

Now it is possible to drill an axial hole through the center portion ofthe fluted element, the hole having a diameter at least great enough tocut out to the root lines of the iiuted element, thereby separating thestructure into four segments. Thereafter, the thread fragments can betapped to form hole titi, and the device is complete. That part of theencapsulating material which lies contiguous to the thread fragments issimultaneously threadtapped, and serves as a gas-seal between thesegments. The rest of the encapsulating material seals between thesegments and the boundaries.

The great simplification of this method of construction overpreviously-required careful assembly and machining techniques forretainer bands, retainer rings, and the like, the necessary precision ofall of which contributed greatly to the expense of manufacturing thedevice, is evident. This manufacturing technique is as simple as pottingan element, and drilling out and tapping a part of it.

In operation, a threaded end of a shank member is threaded into tappedhole 60 in the nut and thereby completely closes chamber 17. Theseparable nut acts as a nut for engagement to a shank member untilseparation is desired. Separation is accomplished by tiring the squib.This releases gases under pressure into the chamber which, as soon assuflicient pressure is generated, begins moving the segments to the leftin FIG. 7 relative to the retainer. Of course this motion is relativeand the segments might be held still while `the retainer moves to theright. Some of the encapsulating material is extruded from the passage,enabling the relative motion of the segments and retainer to take place.After suicient movement, the cam surfaces strike shoulder 22, andadditional movement presses the cam-bearing portions of the segmentsaxially inward toward the shank member, junction 41 acting as afulcrurn. This lifts the thread fragments off the threaded shank member,thereby releasing the same. Relief d@ is smooth and will not interferewith the threads on the shank as it moves away. What happens to thesegments after this point is immaterial. Often they will be heid looselyin the retainer `by the encapsulating material, but this is notnecessary, because they are of no further use.

This device is reliable, easily and relatively inexpensivelymanufactured, and suitable for commercial usages where separablefasteners have never heretofore been feasible because of theirrelatively greater expense.

This invention is not to be limited by the embodiment masas il shown inthe drawings and described in the description which is given by way ofexample and not of limitation but only in accordance withV the scope ofthe appended claims.

I claim:

l. A separable nut for attachment to a threaded shank member, saidseparable nut having an axis, and comprising: a retainer; an interiorwall in said retainer dening a chamber; an axial passage through saidwall in communication with the chamber, the passage having a boundary;an internally projecting shoulder in the chamber adjacent to thepassage; a plurality of axially aligned and radially spaced-apart nutsegments, each comprising a threadbearing portion and a cam-bearingportion; a thread fragment on each thread-bearing portion, saidfragments all being part of the same thread, and which lie on the spiralpath thereof, said thread-bearing fragment being disposed in the passagewith clearances between each other and the boundary, when the segmentsare in a first position, forming a thread means for engagement by thethreaded shank member; a cam surface on each segment extending radiallyoutward when Y.the segments are arranged as aforesaid, and beingrelieved from the thread fragment on the opposite side thereof, all ofsaid cam surfaces lying within the chamber and radially overhanging saidshoulder in the first position; an extrudable encapsulating materialcompletely filling said clearance, bonding the segments in the firstposition by adhesion to the interior wall and to the surfaces of thesegments which face it, there being a full annular layer ofencapsulating material in the radially overlapping region between Itheshoulder and the cam surfaces, and a squib in the chamber, said squibbeing of the type which releases gases when fired to `build up apressure in the chamber; whereby, with a shank member threaded into thesegments to close the chamber, the scub may be fired to expel thesegments from the chamber and passage Contact between the cam surfacesand the shoulder camming the thread fragments off the shank member andfreeing the shank member from the separable nut.v

2. A separable nut according to claim l in which the vsquib is anexplosive squib adapted to re gaseous products of explosion into thechamber'.

3. A separable nut according to claim 1 in which a port vis providedthrough the wall of the chamber, and a squib is threaded into said portin fluid-tight relationship with said wall.

4. A separable nut according to claim 1 in which torque means areprovided on the boundary to resist rotation of the encapsulatingmaterial.

5. A separable nut according to claim 1 in which a tooth is provided onsaid boundary for engaging said encapsulating material to resistrotation thereof.

6. A separable nut according to claim 5 in which a i plurality of teethis provided on said boundary, one of said teeth projecting between themembers of each pair of adjacent segments.

References Cited in the file of this patent UNITED STATES PATENTS1,062,000 Hahn May 20, 1913 1,069,451 Marston Aug. 5, 1913 1,714,316Oakley May 2l, 1929 2,080,850 Prayer May 18, 1937

1. A SEPARABLE NUT FOR ATTACHMENT TO A THREADED SHANK MEMBER, SAIDSEPARABLE NUT HAVING AN AXIS, AND COMPRISING: A RETAINER; AN INTERIORWALL IN SAID RETAINER DEFINING A CHAMBER; AN AXIAL PASSAGE THROUGH SAIDWALL IN COMMUNICATION WITH THE CHAMBER, THE PASSAGE HAVING A BOUNDARY;AN INTERNALLY PROJECTING SHOULDER IN THE CHAMBER ADJACENT TO THEPASSAGE; A PLURALITY OF AXIALLY ALIGNED AND RADIALLY SPACED-APART NUTSEGMENTS, EACH COMPRISING A THREADBEARING PORTION AND A CAM-BEARINGPORTION; A THREAD FRAGMENT ON EACH THREAD-BEARING PORTION, SAIDFRAGMENTS ALL BEING PART OF THE SAME THREAD, AND WHICH LIE ON THE SPIRALPATH THEREOF, SAID THREAD-BEARING FRAGMENT BEING DISPOSED IN THE PASSAGEWITH CLEARANCES BETWEEN EACH OTHER AND THE BOUNDARY, WHEN THE SEGMENTSARE IN A FIRST POSITION, FORMING A THREAD MEANS FOR ENGAGEMENT BY THETHREADED SHANK MEMBER; A CAM SURFACE ON EACH SEGMENT EXTENDING RADIALLYOUTWARD WHEN THE SEGMENTS ARE ARRANGED AS AFORESAID, AND BEING RELIEVEDFROM THE THREAD FRAGMENT ON THE OPPOSITE SIDE THEREOF, ALL OF SAID CAMSURFACES LYING WITHIN THE CHAMBER AND RADIALLY OVERHANING SAID SHOULDERIN THE FIRST POSITION; AN EXTRUDABLE ENCAPSULATING MATERIAL COMPLETELYFILLING SAID CLEARANCE, BONDING THE SEGMENTS IN THE FIRST POSITION BYADHESION TO THE INTERIOR WALL AND TO THE SURFACES OF THE SEGMENTS WHICHFACE IT, THERE BEING A FULL ANNULAR LAYER OF ENCAPSULATING MATERIAL INTHE RADIALLY OVERLAPPING REGION BETWEEN THE SHOULDER AND THE CAMSURFACES, AND A SQUIB IN THE CHAMBER, SAID SQUIB BEING OF THE TYPE WHICHRELEASES GASES WHEN FIRED TO BUILD UP A PRESSURE IN THE CHAMBEAR;WHEREBY, WITH A SHANK MEMBER THREADED INTO THE SEGMENTS TO CLOSE THECHAMBER, THE SCUB MAY BE FIRED TO EXPEL THE SEGMENTS FROM THE CHAMBERAND PASSAGE CONTACT BETWEEN THE CAM SURFACES AND THE SHOULDER CAMMINGTHE THREADED FRAGMENTS OFF THE SHANK MEMBER AND FREEING THE SHANK MEMBERFROM THE SEPARABLE NUT.